A Crazy Ant Invader Uses Acid to Its Advantage

The crazy ant, the latest ant to invade North America, is having remarkable success at replacing its predecessor, the red fire ant, former king of the invaders. Part of the reason, according to research at the University of Texas, is that the newcomer can detoxify fire ant venom in a way not seen before in other insects or animals.

The crazy ant uses its own venom to neutralize that of the fire ant, which is deadly to many other ants and gives the fire ant its notorious sting.

Crazy ants, Nylanderia fulva, are named for their scattershot movements and were first seen in the Houston area and in Florida 12 years ago. They have since been found in Mississippi and Louisiana. They can quickly dominate an ecosystem, wiping out the fire ants that came before them, according to Edward G. LeBrun, who reported the new research Thursday in the journal Science.

Dr. LeBrun and his colleagues Nathan T. Jones and Lawrence E. Gilbert exposed crazy ants to fire ant venom and recorded video of the behavior that followed.The crazy ants engaged in an intense kind of grooming, in which they repeatedly seemed to take their own venom from a pore in their abdomens and spread it all over themselves.

After this behavior, 98 percent of the crazy ants survived. When the scientists blocked the pore that releases the venom, only 48 percent survived.

The researchers did additional tests to prove that the ants were using their own venom and to show that the main ingredient, formic acid, was what detoxified the fire ant venom. They don’t yet know how the detoxification works chemically.

This is not good news for the fire ants, Dr. LeBrun said. The species, he said, are direct competitors and both are “opportunistic, omnivorous, ground foraging.”

“Both feed on carrion,” he said. “Both fight with other ant species to control any resources.” And, he added, “they are also competing for nest space. Fire ants dig elaborate nests. Crazy ants don’t dig, but a great nest site is fire ant mounds.”

The crazy ants are outcompeting the fire ants on all counts — and they have protection against fire ant venom.

Dr. LeBrun said that, for people worried about the spread of crazy ants, human activity is the one thing that limits how fast they spread. Crazy ants only establish new colonies naturally when one gets too big and has to divide. This is a slow process. But if humans move them in wood or potted plants or anything that they are carrying in their cars and trucks, then they spread much faster.

As to the possibility of humans using formic acid as a defense against fire ant stings, Dr. LeBrun wrote in an email, “I’ve tried it. It does not help. In fact it is about as much fun as you might imagine letting a very large fire ant sting you and then smearing acid on the sting would be.”